UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105·3901 

January 10, 2008 

Terrence O'Brien 

Deputy Director for Energy Facility Siting 

California Energy Commission 

1516 Ninth Street 

Sacramento, CA 95814-5512 

Re: Request for U.S. EPA Concurrence Regarding Two Air Quality Amendment RequestsHigh Desert Power Project (97-AFC-O 1) 

Dear Mr. O'Brien: 

This letter is in response to your recent letter, dated October 26,2007, regarding a request 

for revision of the High Desert Power Project ("HDPP") permit, approved by the California 

Energy Commission ("CEC") on October 20, 2004, and a second revision request submitted by 

HDPP dated September 20, 2006. 

EPA issued the initial Prevention of Significant Deterioration CPSD") permit to HDPP 

on February 15,2001. On July 30,2001, in response to a letter from HDPP, EPA issued a 

determination that reconfigurations and other specified changes to the power plant design did not 

affect the terms and conditions of the initial EPA-issued PSD permit. We acknowledge the time 

period for our review of the 2004 and 2006 permit modification requests has been extensive. At 

this time, we have reviewed the requested modifications and will propose the minor PSD permit 

modification for public review within the next several months. This letter addresses the two 

modifications described in your October 26, 2007 letter. Discussions regarding additional 

modifications requested by HDPP, but not addressed in your letter, will not be included here and 

will be discussed in the technical support document for the PSD permit modification. 

Startup and Shutdown Duration and Emission Limits 

The CEC has approved the elimination of durational limits on startups and shutdowns 

CS/S") while leaving all emission limits unchanged. Although not explicitly stated in your letter, 

the CEC approval, dated October 20, 2004, also allows the "per turbine" SIS emission limits to 

be combined for all three turbines by multiplying the per turbine limit by three. The EPA-issued 

PSD permit includes the durational limits for SIS on a per turbine basis. These limits constitute 

the SIS portion of the Best Available Control Technology CBACT") determination for the 

HDPP PSD permit. As such, a requested relaxation of BACT must be justified by HDPP. 

Although HDPP contends that this modification would provide flexibility during startup and 

would not change the air quality impact analyses from the initial PSD permit, HDPP has not 

provided adequate justification to relax this BACT determination. Your letter states that CEC 

staff and staff at the Mojave Desert Air Quality Management District CDistrict") have 

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determined that this modification would allow HDPP to start their turbines sequentially in order 

to minimize thermal stress on the combustion turbines and steam turbine. 

HDPP is configured with three combustion turbines ("CT"), each with a dedicated heat 

recovery steam generator ("HRSG"). Each CT+HRSG unit feeds into one steam turbine 

generator ("STG"). Each unit has an individual SIS limit based on pounds ("Ib") of pollutant 

emitted per event, and an individual allowable startup duration depending on the condition of 

startup (i.e., cold, warm, hot start). Emission limits and durationallimits apply to each 

CT+HRSG unit individually; therefore, each unit is already permitted to startup sequentially. 

Because the requested modification relaxes an existing BACT determination, and the applicant 

has not supplied adequate justification for removing the SIS duration limits, we do not plan to act 

on this specific request. 

On November 8, 2007, Anita Lee, of my staff, discussed the requested modifications with 

Jon Boyer, of HDPP. Mr. Boyer raised an additional concern regarding the SIS duration limits 

when the turbine "trips" during startup. This issue was not discussed in the 2004 or 2006 PSD 

permit modification requests, however we will continue working with HDPP to address this 

concern before proposing the PSD permit modification. 

NO! and CO Performance Test Frequency 

Your letter additionally discusses a request from HDPP to extend the frequency for 

oxides of nitrogen ("NOx " ) and carbon monoxide ("CO") source testing from every year to every 

five years. HDPP believes that the existing Continuous Emissions Monitoring Systems 

("CEMs") for NOx and CO, and the required annual Relative Accuracy Test Audits (RATA), 

would ensure adequate determinations of compliance with the NOx and CO emission limits. EPA 

plans to act on this requested modification, and will include a condition that requires the source 

testing frequency for CO and/or NOx to return to every year in the event of a fai led RATA for 

the CO or NOx CEMS. 

If you have any questions or need additional information, please contact Anita Lee at 

(415) 972-3958, or at lee.anita@epa.gov. EPA will notify CEC, the District, and HDPP when the 

PSD permit modification for HDPP is proposed for public review. 

Sincerely, 

/

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Gerardo C. Rios 

Chief, Air Permits Office 

Cc:	 Jon Boyer, High Desert Power Project, LLC 

Alan De Salvio, Mojave Desert Air Quality Management District